Back plate



FIG. 1 is a front elevational view of a back plate embodying my new design;

FIG. 2 is a side elevational view thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a bottom plan view thereof.

FIG. 5 is a sectional view through FIG. 1 on the plane of the line 5--5. 

The ornamental design for a back plate, as shown and described. 